blindfly

Just wondering if there are any...
I you did - please tell me why, since manufactors ask to fly the engines to break-in.

Oh, another thing - did any of you "fly to break-in" had any problems with the engines during that time?

(flame-outs, bad transsitions ets)

Ed

I'll run it on the bench for a tank, or two. It allows me to tweak the needles to a good safe setting, and develop a good starting routine. I think that is reason enough to run it on the bench. It saves a lot of hassle at the field later.

> Jim

famousdave

My Feedback: (61)

Its far better to break in gas engines in the air than on the bench.. there simply is not enough cooling air making it past the engine to keep temps down during break in. .. also the prop load helps break it in faster. ... fly with the cowl off the first few flights. If a gas engine does not run reliably out of the gate something is wrong with it...

I have seen people burn up good engines by running them on the bench too long..

DP

Tired Old Man

My Feedback: (1)

I also run a tank or two through either on the bench, or on an un-cowled airframe prior to the first flight for the same reasons as GeeBeeJim. After that, it's all done in the air. To trust absolutely to a manufactures carb settings for the first run/flight could well be suicidal for the aircraft.

Nogyro

My Feedback: (10)

I do mine in the air. Crank it up, set the low needle for good idle and transition. Slowly advance throttle to full throttle. If it's not blubbering rich on the top end, I'll run it up and down a few more times, go out and taxi for a minute or so, if everything sounds good, put it in the air. I stay in close to the field, but high enough so that just in case it does quit, I'm in good shape for a dead stick landing. ( I've never had that happen though) Don't do any prop hanging, just nice boring stuff. Stay up 10 minutes or so and land. Go over EVERYTHING real well. If it checks out, fly again but still take it easy.

Albatross

My Feedback: (7)

I have done both methods.

I break in my BME44 in the plane; however I ran one tank on the ground; then I flew the airplane without installing the cowl. Then I installed the cowl after the 3rd flight.

I did the same thing with my ZDZ50 last summer; however 1 month ago; when I replaced the piston ring and cylinder (due to a muffler/ cylinder problem) I had to start all over again the break-inn for this newly set.

I think break-in in the air is by far the best way to go.

However this time I decide to use the breakin bench approach. Knowing that the lack of enough circulating air can potentially affect the engine rather than help due to the stationary airflow, I decide to monitor the temperature of the engine during the process.

I wanted to concentrate my temperature readings on the head cylinder area.

Under this conditions, the higher the rpm the higher the temperature. More likely in the air the engine behaves the same way but in less degree.

@ 4000 rpm the head temperature reading was around 270F
I decide to increase the rpms after 1 gallon @ 5000 rpm the temperature reached almost 330 or more. At that point I throttle back to idle allowing the engine to cool down using the same airflow form the idling engine. I repeated this cycles multiple times; so that I was watching for high peaks of temperature rather than high rpm. Note never went to full throttle under this conditions.

I decide to go with these experiments in order to have some data about the progress of cylinder temperature.

blindfly

what if you put a large fan in front of the engine while running on the banch?
i believe it will give it the cooling it needs and somewhat simulate running through airflow...

- the needle access issue is a good one!

rmh

no-
flying reduces the engine load -that is what is doing the cooling.

famousdave

My Feedback: (61)

Dick -

I guess my wording was a little confusing...
You are correct in that the overall load while flying is less (its a lot easier on the engine to pull a plane than trying to move a stationary bench) but the bearing loads and up-down throttle movements during a flight precipitate a faster break in than a bench run and the engine runs much cooler due to a decent airflow over it (and probably less load as you mention)...

I have rarely seen CHT over 180 - Albatross said he's seen 270 as CHT... either his gauge or his engine's cooked.

I only had one engine ever get close to 270, and that was a ZDZ that had a failing front bearing. It finally locked up in flight.. engine temp was about 260 after a slight cool down during the resulting dead stick.

I thought the rule was one should never be able to boil water, spit, etc on a cylinder head or case - if you can - the engine is way too hot (over 220 any way)..

DP

Volfy

My Feedback: (23)

I don't see how running an engine on the bench with a big 'ole fan (i.e. the prop) in front of it would ever overheat it to a point of causing damage.

First off, the proper place to measure engine temp is directly on top of the cyl head near the spark plug. Any other place on the engine will produce readings that are not as indicative of engine operating conditions.

Secondly, if you are taking temp readings with one of those infrared temp guns, then your readings can be way off actual. A shiny aluminum cyl head does not a perfect black body radiator make. Since most of us are not inclined to spray paint the top of that purdy DA50 flat black, the most accurate temp reading is done with calibrated thermocouples. I do have a Raytek temp gun - one with a laser dot sight - and as good it is for some other applications, it can sometimes read as much as 50F off thermocouple readings on engines. 300F near the spark plug is not uncommon for an aircooled 2stroke gasser. 350F on a hot humid summer day is no cause for alarm either.

Thirdly, if loading the engine during break in is a concern, as it should be, then one can easily use a smaller prop. Most manufacturers recommend such practice, no?

Fourthly, what the engine manufacturer recommends is always good for the engine. Ask the airplane manufacturer, however, and you are liable to get a different answer. Running in an unfamiliar engine initially on the bench to get the needle setting correctly will save your expensive airframe from enduring the same sitting on the ground, where it gets absolutely no benefit from the air mass vibration dampening it gets when flying through the air.

Besides setting the needle valves and generally "loosening up" a just-out-of-box engine, running the engine on the bench is great for tuning pipes and "benchmarking" (pun fully intended) performance of an engine. Beyond that, the remainder of the break-in is most definitely best done in the air.

Albatross

My Feedback: (7)

I have monitored the temperature of the head as the break-in progress; the temperature readings are trending down; one day after running the engine on the bench the head temperatures were in the neighborhood of the 200; perhaps less. In effect by now the readings are around 190's F. I was able to afford one of those IR thermometers in Sears; of course buying a telemetry system to know the actual temperature during all working conditions, is not in my list of priorities at this moment. Once the engine was mounted on the airplane, the data that I am referring here was obtained right after landing.
One note aside: the giant glow engines seem to run cooler than the similar size gas engines. The same day my friend JoeAirport was testing his Moki 1.8 on the ground, I garbed my thermometer to check his temperature engine, it was only 180 F or less.

BBW Walt

My Feedback: (11)

Volfy's got the heads up on this one. I have seen several 300 deg. temps on test run ups. This temp is a no issue. The only accurate reading I have been able to get is next to the plug. Or maybe better said consistant reading. I test run all mine for a comfort thing. I usually run 2 full run up and cool downs, usually this puts maybe 15 minutes total on the engine, and its all set to go..Go to the 3W web site and see what they recommend for break in. 10-20hrs on the stand.

Richard L.

My Feedback: (24)

Yes, nitro keeps the combustion chamber cooler. The higher the nitro content, the cooler the engine will run. This is true for smaller glow engines as well.

famousdave

My Feedback: (61)

I use an RCATS telemetry setup -- two thermocouples - one on the head at the plug, the other at the cylinder base.. I consistently get a 160* case temp and 180* cylinder temp on my 3W 75 and 3W-24. I have a DA-50 that runs a few degrees hotter, but there is less metal to dissipate heat and its not broken in yet.

I have rarely seen an engine go above 200, even during our 110+ degree days.

Since this is a gas engine forum, I am assuming we are all discussing gas. Glow engines can run all day on the bench. They won't have cooling problems because you can run them super cool and rich.

DP

rmh

FWIW- I do all of my muffler tests /pipe setups on my bench- but I never just let the engine wail away at full tilt for more than a few seconds -
IF---I was doing a max thermal soak and temp check -- then I would run it that way. for example -
If you intend to take off and hover at full throttle for the entire flite of 30 minutes - a bench check of full throttle for 30 minutes should provide accurate info.
When guys do rpm checks - they should compare using same technique used by the knowledgeable engine mfgrs
the engine is adjusted for best setup - cooled , then read as engine is run up on the next sequence.
IF----you run up the engine to full - it should be possible to hear the transition from a rich setting to ideal mix for the load ---as the engine heats. and you record the peak.
IF---- you keep on running at full rpm -the tach should gradually drop rpm about 100-300 (depends on prop/load / high tide/ etc..
If you keep on - the temp will likely start a faster rise as the engine thoroughly heats
The problem now CAN become thermal runaway.
This is a condition where the engine cooling ability falls behind the heat being input by the load .
IF--- there was a closed loop FI setup -like autos now use -- the injectors would ad fuel -to cool things down.
The best we can do is to try to establish what the actual air load will be and set needles for that condition.
Many guys have been tricked by this and have destroyed an engine which they though "sounded OK when they took off".
The temp -if using an infra red pointed at the cyl about the upper region should give you the best area to record for future comparison.
All of my setups must run under 200 f ,when checked in this fashion.
If I attached a thermocouple to the plug base - I am sure I would get a different reading - but I want to have info I can use from the bench to the flying field.

Diablo-RCU

My Feedback: (1)

You would think the manufacturers would add a few more cooling fins and increase their area to keep the engines cooler. A few more fins wouldn't add much weight. Considering the skills(?) of the average modeler with engine needle tweaking and air flow in the cowl, the increased cooling capacity might prevent a lot of warranty repair from cooked motors.

3D Joy

If the BME 110 was as heavy than the DA 100 due to added cooling fins, then BME would not sell any engines.

rmh

Fins may not be the the real problem
the first generation of ZDZ singles had more fins (area).
I have not run any of my own engines for full load extended full throttle runs on the bench. and do not expect to do so.
I still see clowns at the flying field with a model strapped to a post and letting it run full tilt till the tank goes dry - thank God these are isolated occurrances.
And they are typically smaller glow setups .
It is hard not to go suggest that there are better procedures -----
Our model use of these gassers is typically NOT the same as the industrial conversions.
Those are (my opinion) better suited to a flat out extended hot running.
They are also heavier - bigger cranks/bearings/ different materials etc., etc..
There really is a need for better airflow setups tho - twins especially when run on 3D setups and hovered (yawn) endlessly - can get smoked.
Newbies , who switch from the glow plug setup and fly with the throttle at full volume for the entire flight can easily wreck a new engine.
The glow setups had to be cranked down to the point of the engine quitting in flight -to cause real problems . Not so on the gassers - they will melt.
All part of the learning curve--

Flypaper 2

Engine fin area is related to what the engine needs to run at for efficiency. Engine running to cold will have accelerated wear and poor fuel vaporization and plug fouling. Don't need to say what an overheated engine will do. On the snowmobile engines I used to work on, the average running temp with a thermocouple under the plug washer, was 350 F. As you say Dick, cowl ducting could be made better of as in full size practice.

Volfy

My Feedback: (23)

Dick, have to disagree with you. I know of no auto FI EMS systems that enrichen the mixture to lower engine temp. Most modern closed-loop controls are all variations to factory pre-programmed mapping based on two main themes:

1. Fuel mixture control based on Lambda (oxygen) sensor feedback
2. Ignition timing control based on knock sensor(s) feedback

These are fine-tunning parameters in addtion to the main intake air mass flow meter. For emission control, EMS usually stays very close to the stochiometric 14.7:1 through out most engine operating condition. Most EMS does have programming to guard against overheating damage, but it does this by cutting fuel completely - NOT adding fuel. Adding fuel past stochiometric does not cool the engine any, but begins to increase CO and NOx production dramatically. On the other hand, no fuel = no combustion = no heat added = slowing down to a creep on the side of the road, which is prefrerable to continued running the overheated engine and trying to mess with mixture control. Besides, the water jacket in the typical auto engine would buffer any modulation of the fuel mixture in an attempt to control engine temp. This lengthens the deadtime in the response such that closed loop control is inpractical.

Most auto EMS do employ a throttle postion switch to enrich the fuel mixture slightly at WOT. Engines typically product max power at lightly above stochiometric. Emissions may suffer a little, but excusable when the driver slams the pedal to the metal.

Going back to RC gassers... well, it doesn't matter how they chrome 'em, polish 'em or paint 'em, most RC gasoline engine cylinders start out life in the casting foundries of Zenoah, Makita, Sachs Dolmar, Husky, etc., right next to their industrial engine brethrens. These things are designed to run full bore insides of chainsaws, blowers and pumps for hours on end, with nothing but the flywheel fan to keep cool and enduring punishing heavy and sometimes shock loads. Turning a little propeller at fairly constant and light air loads is like vacation on Tahitian beach for these critters.

The obviously exceptions are, of course, the likes of ZDZ, RCS, some MVVS and a handful of other genuinely designed-for-RC gassers. I would have to go on faith that their designers took the very popular 3D application into consideration when appopriating cooling loads.

BTW, if you are only measuring 200F on a gasser running at anything other than around idle, either you are not measuring it right, or you are doing so at ambient below 50F. Heck, my glow engines get above 200 easily, and approach 275~300F on a Houston summer day. Gasoline engines run quite a bit hotter than glow engines. To get an accurate reading, you must make sure the thermocouple makes good contact with the cylinder metal and shielded somewhat from the prop blast. Otherwise, the thermocouple gets insufficient heat transfer from the engine and too much cooling airflow. A good place to stick the probe is right behind the sparkplug.

Two ways to check if your readings are too cool:

1. Check it against an infrared gun. If the gun read higher, then your TC is not set up correctly.
2. Get the engine RPM up for more than 30sec, then shut off the engine and read the temp. IF it climbs more than a few degrees, your setup is wrong.

Air is a great insulator, so even a little air gap between the TC and the engine is enough to skew the reading. Press that TC firmly against the base metal.

In any case, the deciding test is: if your engine runs on the bench and holds its cyl head temp, then that setup is perfectly fine to running indefinitely. Besides, unlike glow engines, gasser don't need to be run at WOT for break in. So running in the gasser on the bench at various part throttle positions should be no concern at all.

rmh

I do understand your comments
Note tho -you mentioned WOT enrichment - -that is what I was addressing.
Also, one can reprogram FI (for NO2 and turbo apps ) which add fuel to correct the burn. (std rice burner hop up stuff)
Adding fuel does help cool -it prevents detonation which sets up runaway temp- I have plenty of past experience with race engines to back up that fact.
I did not mean to infer that the computer poured in fuel to stop a huge imbalance of heat.
loss of water -sets up "limp home" as you noted.
My temp readings as noted are "referrence" temps - One I can read by poking a gun at the front of various engines
It ain't perfect but it gives a quick, reliable referrence.
An EGT or plug thermocouple is more accurate sure - but for our stuff a comparative referrence fits the job.

Futurase

My Feedback: (10)

I am going to ask a real stupid question for a lot of you engine guru's. We do not pet and baby a new chainsaw when we get it and no one will ever convince me a airplane enviroment is a harder load and yet they do not over heat in hard, long use in the hot summer time and all everyone talks about is how much you need to baby our engines. I have a DA and Zenoah and I am doing the break-in like DA says to. I think we baby the things way to much as most all engines are from a chainsaw or etc except for the DA's, 3W's and etc. If the general populus had to baby every chainsaw and weedeater like we are told to then Stihl and everyone else would go bankrupt!!!

Running a single cylinder is not going to hurt it at all on the bench as long as it is not lean. Yes flying it in the air does unload it some there is no doubt, but the things are not near that fragile. If they were then who would want one. I am no convinced that a twin will be hurt by bench running either. That being said I have never seen a twin that needed running on the bench. They are going to be a lot smoother due to them being a twin and not need the break-in on a bench. My DA 50 was ran on the bench for 6 tanks and DID benefit from it as the idle improved noticably. I kept a monitor on temps and it runs every ounce as hot after a flight as it did on the bench. Never breaks 170 and that was after a lot of long sustained verticals and some hovering. Never breaks 165 on the bench. A chainsaw gets hotter than that by far as all it has for cooling is a crank fan and the fuel. I have a Stihl that is 8 years old and runs like a clock and fires the first time you pull it. I'd hate to know how many truck loads of wood it has cut.

The main thing is not to have it over propped and the needles set to lean. That will burn anyhting up, but if both are set right you can run it on the bench just fine. You take a chain saw out of the box, fuel it up and go cut with it. Mine has just gotten stronger as it has been run too. Bench running hurts one when you have a bad oil ratio or poor quality oil and too big a prop and/or lean needles.

Norman Ross Jr.

JohnVH

My Feedback: (38)

Never run engines on bench, always put in plane, adjust so runs reliably, then fly it.

RTK

My Feedback: (1)

John, not to be argumentative but I read 3W's had bench running involved and a lot of it. Another engine manufacturer told me to let the engine idle or just above idle for about 30 minutes.

cknaack

My Feedback: (1)

RTK,

I have a 3W 75 that is going into a P-40. Upon review of the instructions, I first read that 3W recommended bench running as you indicated. Reading on further, I saw a reference to avoid bench running. It was confusing to say the least.
In the past, I have always bench tested my gassers before mounting them on an airframe. It's just my preference to gain a bit of confidence in an engine, and to ensure that the needles are set correctly. I did have some grief once during a Q50 bench break in. I could not get the engine to run below 1/2 throttle. After a good bit of screwing around, I finally figured the problem out. I had the butterfly turned to the wrong position, preventing the low side of the carb from drawing fuel. I would have had a hell of a time finding that in the cowl of my P-47!

I'll continue to run a few tanks through my gassers on the bench, just to be on the safe side.